1. Field of the Invention
The invention relates to a novel surface heating system, a heatable object with the novel surface heating system and a method for producing the novel surface heating system. More particularly, this invention relates to a seat heating system, a heated seat and a method for producing it. Preferably, the invention additionally relates to a heating system for side panels and floor coverings, in particular in motor vehicles, side panels and floor coverings outfitted with such heating system in particular in motor vehicles and a method for producing them. Furthermore, this invention relates in particular to a mattress heating system, a heated mattress and a method for producing it.
2. Prior Art
Seat heating systems are known from practice, for example, for motor vehicles; these systems in the sense of the invention are a surface heating system and are formed by current-carrying metallic conductors as heating wires that are arranged between cushion layers. This necessitates not only a costly construction of an appropriately designed seat, but it also has disadvantages in particular in operation. For instance, because of the stronger heating of surrounding layers in the immediate vicinity of the heating wires there is a danger of overheating, which can lead to damage to the cushion layers and/or the heating wires and even cause a fire. Furthermore, the heat distribution over the area is not optimum, since the temperature is always higher in the region of the heating wires than at a distance from them. Also disadvantageous with this known style is the mechanical stress to which the heating wires are subjected when a passenger uses the seat, since the conducting wires can break because of this, which can lead to failure of operation and/or can have as a consequence another source of fire.
A composite heating element that provides a directed heat radiation and is formed of a plastic laminate with incorporation of a semiconducting layer is known from DT 26 16 771 A1. This laminate consists of a hard plastic laminate structure that is formed of at least one layer of a reinforced substrate base material and a resin coating on this material, a semiconducting carbon containing a pyropolymer, which is bonded to a heat resistant inorganic oxide support with large surface area, which is incorporated as a layer on at least one side of the layer of the substrate material, a heat reflecting layer incorporated on the substrate material in a position on one side of the pyropolymer, and power supply devices to spaced parts of the layer of conductive carbon-containing pyropolymer, and which produces electrical resistance heating in the laminate, which is reflected and radiated by the heat reflecting layer of the laminated element. Such heating panels are intended to be used as part of a wall of a living space or office.
With this prior art the incorporation of the semiconducting layer into the laminate can take place by mixing finely divided carbon-containing pyropolymer in the form of small particles or as powder with a suitable carrier or vehicle, which can be brushed, spread or otherwise applied to the surface of a resin coated glass cloth of paper, felt, cardboard and the like as laminate substrate or to a wood veneer that is used in the laminate panel. Instead of this, the finely divided carbon-containing pyropolymer can also be mixed with the resin or polymer material with which a particular reinforcing base material is to be impregnated or that is to be applied to this base material as a coating, where this base material provides at least one substrate material of the laminate. The resulting mixture is applied into or onto the substrate by immersion or coating, and the resulting coated substrate is subjected to a semi-hardening such that the semiconducting pyropolymer produces a uniform impregnation and coating over the resulting semi-hardened laminate sheet.
DE 33 16 182 A1 concerns the use of molded articles like films, or panels or three dimensionally shaped articles from the class of the pyrrole polymers that are complexed with anions, as electrical heating elements in particular for heating corroding liquids or gases. The molded articles can also be coated with organic plastics.
A polymer composite heating element is described in DE 35 24 631 A1 and has the form of a film, tube or rod. Such polymer composite heating elements can be used as heating elements as such or can be laminated with traditional plastic films in order to improve the strength of the material.
The use of electrically conductive thermoplastic polyurethanes and their preparation are known from DE 33 21 516 A1. The corresponding products are suitable, among other things, for the preparation of 1–2 mm thick films for surface heating elements.
Thus, heating elements with electrically conductive plastic are indeed known, but in all of the prior art there is no data or hints of how such heating elements are to be designed and produced in order to be able to use them in practice.
Surface heating systems that have a layer of electrically conductive plastics are illustrated in a number of other publications of the international patent classes H05B 3/36 and 3/84 using the outside mirrors of motor vehicles as examples. Essentially, films of electrically conductive plastics on solid supports are used in this case. The use of a film of electrically conductive plastics on the support structure of a vehicle seat, however, is not possible, since all the cushion layers lying on top, etc., would have to be heated for the heat to reach a sitting passenger, which would involve a great deal of energy.
In particular for sitting or reclining supports there are no known usable surface heating systems with electrically conductive plastics. However, simple, inexpensive and safe heating systems would be desired, for example, for vehicle seats or mattresses.